Supplementary Material for: Metabolic Dynamics in the Prefrontal Cortex during a Working Memory Task in Young Adult Smokers

<b><i>Introduction:</i></b> Cigarette smoking is known to modulate brain metabolism and brain function. How the dynamics of these metabolic alterations influence the active performance of higher order cognitive tasks in smokers, compared to non-smokers, is still unclear. The present exploratory study sought to examine the impact of smoking on the “complete” metabolic profile while the participants performed a working memory (N-back) task. <b><i>Methods:</i></b> The study sample consisted of 40 young male healthy participants (smokers [<i>n</i> = 20] and non-smokers [<i>n</i> = 20]). Functional magnetic resonance spectroscopy data were acquired using a 3 T whole-body MR system. Data analysis was performed using Java-based Magnetic Resonance User Interface software, and metabolite ratios with respect to creatine (Cr) were calculated. <b><i>Results:</i></b> On a behavioural level, smokers showed worse performance (measured by d’) than non-smokers. However, we observed significant differences in the metabolite concentrations in smokers compared to non-smokers, which also changed over the course of the N-back task. A significant effect of the group was observed with smokers showing lower glutamate/Cr (Glx/Cr) and choline/Cr (Cho/Cr) ratios than non-smokers. Further, N-acetyl aspartate (NAA/Cr) and Cho/Cr ratios were significantly different during the rest and the task conditions. In addition, our results demonstrated the metabolite interactions (NAA and Cho, Glx and myo-inositol [mI], and Cho and mI). <b><i>Conclusion:</i></b> Further studies are necessary to shed more light on the association between smoking behaviours and metabolic alterations. However, our preliminary findings would assist in this future research to have a complete understanding of the metabolite interactions not only in smoking but also in addiction research.**<i>引言：</i>** 众所周知，吸烟可调节大脑代谢与脑功能。然而，与非吸烟者相比，这类代谢改变的动态过程如何影响吸烟者执行高级认知任务的作业表现，目前仍不明确。本探索性研究旨在考察受试者在执行N-back工作记忆任务时，吸烟对其“完整”代谢谱的影响。**<i>方法：</i>** 本研究样本共纳入40名年轻健康男性受试者，其中吸烟者20名、非吸烟者20名。采用3 T全身磁共振系统采集功能磁共振波谱（functional magnetic resonance spectroscopy）数据。数据分析基于Java开发的磁共振用户界面（Magnetic Resonance User Interface）软件完成，并计算了以肌酸（creatine，Cr）为内参的代谢物比值。**<i>结果：</i>** 在行为学层面，吸烟者的作业表现（以d’值衡量）较非吸烟者更差。然而，与非吸烟者相比，吸烟者的代谢物浓度存在显著差异，且该差异随N-back任务进程发生动态变化。组间效应显著：吸烟者的谷氨酸/肌酸（glutamate/Cr，Glx/Cr）比值与胆碱/肌酸（choline/Cr，Cho/Cr）比值均低于非吸烟者。此外，静息状态与任务状态下的N-乙酰天门冬氨酸/肌酸（N-acetyl aspartate，NAA/Cr）比值与Cho/Cr比值均存在显著差异。进一步分析还揭示了多组代谢物间的相互作用：NAA与Cho、Glx与肌醇（myo-inositol，mI）以及Cho与mI之间的相互作用。**<i>结论：</i>** 未来仍需开展更多研究以进一步阐明吸烟行为与代谢改变之间的关联。不过，本研究的初步发现可为未来相关研究提供重要参考，助力学界全面理解吸烟及成瘾研究领域中的代谢物相互作用机制。